Perfectly balanced vibrationless rotation-reciprocation devices of crankshaft rotary motion system

ABSTRACT

A perfectly balanced rotation-reciprocation device providing a rod rotatably supported by a crank pin of a crankshaft through an eccentric collar and cooperating means to produce linear reciprocating motion of the rod, the device further providing balance weight means to theoretically balance the caused unbalance forces irrespective to the fact that the balance weights are secured asymmetrically to the longitudinal axis of the rod.

United StatesPatent lnventor Kenjiro Ishida No. 22-22,l-Chome, Hirosawa-cho, Hamamatsu, Japan Appl. No. 839,956

Filed July 8, 1969 Patented Feb. 16, 1971 Priority July 16, 1968, July 16, 1968 Japan 43/49657 and 43/49658 PERFECTLY BALANCED VIBRATION LESS ROTATION-RECIPROCATION DEVICES 0F CRANKSHAFT ROTARY MOTION SYSTEM 4 Claims, 8 Drawing Figs.

0.8. CI 123/192, 74/49, 74/603, 123/197 Int. Cl. ..F02b 75/06, F02b 75/32 Field of Search 74/49, 50, 603,604; 123/192, 192 (B), 197, 197 (AA), 197 (AB), 197 (AC) Primary Examiner--Wendell E. Burns Attorneys-Robert E. Burns and Emmanuel J. Lobato ABSTRACT: A perfectly balanced rotation-reciprocation device providing a rod rotatably supported by a crank pin of a crankshaft through an eccentric collar and cooperating means to produce linear reciprocating motion of the rod, the device further providing balance weight means to theoretically balance the caused unbalance forces irrespective to the fact that the balance weights are secured asymmetrically to the longitudinal axis of the rod.

RECIPROCATION DEVICES OF CRANKSHAFT ROTARY MOTION SYSTEM The present invention relates to a rotation-reciprocation device and more particularly to a perfectly balanced reciprocating machine or machine part combined by reciprocating motion and uniform speedcircular motion.

Known piston-crank device or rotation-reciprocation device such as internal combustion engine inevitably accompanies vibration as the unbalanced forces caused by inertia of reciprocating mass such as piston and connecting rod cannot be balanced theoretically. The vibration causes known hazards, according to an increase of the number of revolution or the torque.

The primary object of the present invention is to eliminate such disadvantages and to provide a perfectly balanced vibrationless rotation-reciprocation device which theoretically eliminates unbalance force of the reciprocating mass which has been assumed inevitable to such kind of devices heretofore.

In order to attain above-mentioned object, the perfectly balanced vibrationless rotation-reciprocation device, according to the present invention, has its feature to comprise a casing, a rod having working means at one end, an eccentric collar means rotatably supporting the other end portion of said rod and having an opening at eccentricity I from the center of the collar, a crankshaft rotatablys'upported by the casing and rotatably supporting the openin'gof the collar means by a crankpin having eccentricity 1, means to cooperate said eccentric collar means and said crankshaft torotate said crankshaft and collar means at the same angularvelocity and in the reverse direction each other and to effect linear reciprocating motion of the rod, balance weight means having weights W and W respectively secured to the eccentric collar in the oppositeside of the center of the eccentric collar at distances R and R to the axis of the crankpin and at distances (L,-l,) and I, from longitudinal axis of the rod respectively, another balance weight means having weights W and W respectively secured to each crank arms of the crankshaft in the opposite side of the crankpin at distances R and R, from the axis of the crankshaft and at distances (Lg-l and 1 from the longitudinal axis of the rod respectively, and said both balance weight means being determined to satisfy formulae W0l= W 12, W,R, L, W,R, 1, W01 (W,,+ W, W,+ W,)l= W R,+ W R, L,W,R W,,+ W,+ W,+ W -,)l wherein,

W reciprocating weight W, rotating weight L, distance between centers of gravity of W, and W, L, distance between centers of gravity of W, and W so that unbalanced forces caused by reciprocating mass are balanced.

As mentioned above, the rotation-reciprocation device ac- Further as the rod to connect piston or working means performs linear reciprocating motion, the rod receives only compression load and no bending moment acts to the rod, also no side pressure is applied to the cylinder.

The above-mentioned features of the perfectly balanced vibrationless rotation-reciprocation device according to the present invention can be utilized in many applications as prime movers, such as internal combustion engines or hot gas engines and also as working machines or mechanisms driven 0 by other input power source. Some of the applications will be cording to the present invention provides a linearly reciprocating rod, a rotating crankshaft, an eccentric collar supporting the rod and rotating and revolving on the crankpin, and cooperating means to produce linear reciprocation of the rod. The device further provides balance weight means according to the present invention, as will be explained more fully hereinafter, which theoretically balances all unbalance forces. The construction is veryrsimple and need not to add much parts to the conventional crank and rod mechanism. The vibration amplitude characteristic of the device according to the present invention is in the order of 3 to 4p. at 5,000 r.p.m. of the crankshaft, the value is about one-eightieth to conventional crank and rod device.

The balance weight can be determined veryeasily and need not secure symmetrically to the longitudinal axis of the rod, so that the versatility of utilization of the device is furthermore increased.

mentioned below.

At first the vibrationless feature can advantageously be utilized as machines which are not to be mounted on rigid foundation. Such applications include portable gasoline engines for many uses such as chain saw, mower, branch cutter or sprayer; and also soft foundation engines for vehicles such as boats, motorcycles, automobiles, airplanes or lawn mowers.

The feature of the vibrationless linearly reciprocating rod can be advantageously utilized as prime movers and working machines. As prime movers, both sides of the piston can be utilized as double acting engine or underside of the piston can be utilized as precompression space for intake of gas mixture or air especially for two-cycle engine. As compressors, double-acting or two-stage compressor can easily be attained. Further, the connecting rod can be divided to insert spring means for accommodating torque variation or to insert adjustable means to vary compression ratio.

The linear reciprocating feature also can be utilized as working machines or mechanisms driven by other input source. Such applications include needle bar mechanism for sewing machine, reciprocating mechanism for spinning and weaving machine, spring expansion mechanism for spring testing machine, reciprocating mechanism for machine tools, riveters, chisels, or hammers.

Principles, mechanisms, features and advantages of the present invention will become apparent in the following detailed description referring to the accompanying drawings, in which:

FIG. 1 shows a locus diagram of a point on a periphery of a disc D. which rotates on its axis at a constant angular velocity and revolves at the same constant angular velocity in the reverse direction;

FIG. 2 shows a diagram illustrating each moving mass projected on X-Yplane; Y I

FIG. 3 shows a diagram illustrating rotating masses shown in FIG. 2 projected on X-Yplane;

FIG. 4 showsja diagram illustrating revolving masses shown in FIG. 2 projected on X-Y plane;

FIG. 5 shows a longitudinal sectional view along line A-A of FIG. 6 showing a crankshaft rotating eccentric geared perfectly balanced two-cycle reciprocating engine embodying the present invention;

FIG. 6 shows a partially broken away side view of the engine shown in FIG. 5; I

FIG. 7 shows a longitudinal sectional view of a crankshaft rotating internal geared perfectly balanced two-cycle reciprocating engine embodying the present invention; and

FIG. 8 shows a sectional view along line B-B of FIG. 7.

At first, theoretical analysis of basic principle about generation of linear reciprocating motion by combining two uniform speed circular motions will be explained.

As shown in FIG. 1, a disc D rotates on its axis 0, at constant angular velocity or, and at the same time the point 0, revolves on a center 0 at distance I at the constant angular velocity u) in the reverse direction with the disc, then every points on the periphery of the disc D at radius I perform linear reciprocating motion through the point 0. That is, when a crank 00, rotates on the axis 0 at constant angular velocity or, and a link 0,0, rotates on the crankpin O, at constant angular velocity or in the reverse direction of the crank, the point 0 performs linear reciprocating motion along line O-X at stroke 41 by rotation and revolution of the link 0,0

Theoretical principle of the perfect balancing of the abovementioned mechanism is as follows:

In the description, it is assumed that, rotation members rotate at constant angular velocity, and that frictional forces between members and effects of play between shafts and bearings are neglected.

As shown in FIG. 2, when,

A center of gravity of rotation balance weight B center of gravity of revolution balance weight C center of gravity of reciprocating mass revolution center 0, rotation center 0 center of big end of connecting rod W reciprocating weights (sum of mass as piston, connecting rod, and reciprocating parts of crank 0,0

W, weight of rotation balance weight W weight of revolution balance weight W rotation weight except W and W,

3 acceleration of gravity R, vector showing position of point A from center 0,

R vector showing position of point B from center 0 I distance between centers 0 and 0,

P vector showing position of point C from center 0 Inertia force F acting to the reciprocating mass F= 00 mour =2? w cos 0 is obtained as follows: Position vector of point A is OA=00,+0,A=I '"+R,e =le "R,e; Inertia force F, acting to point A is Inertia force F 2 acting to revolution balance mass is obtained as follows: Position vector of point B is OB=R i( +6)=.- R j i Inertia force F 2 acting to point B is V (5) Inertia force F, acting to rotation mass 3 m g is obtained as follows: Position vector of point 0, is

O0,=le 0 (6) Inertia force F 3 acting to point 0, is

F3 we Sum of the forces must be zero at balanced condition, thus, F+F,+F +F Other condition to obtain perfect balance is balancing of moment of inertia force. Moment of inertia force M about rotational center 0, is

as formula (9), W,,l=W,R, M01=0 In this mechanism, extension lines of inertia forces F F and F are all pass through the point 0, moment of inertia forces about point 0 are all zero. Moment M, of inertia forces F, about revolution center 0 is W, ;9 1B 2 1fl "10 M (le R16 g to (Z6 R e 0 (12) Thus, extension of the inertia force F, acting to the rotation balance mass passes through point 0. Consequently, moment of inertia forces about axis Z are perfectly balanced.

As stated above, when balancing condition shown in formulas (9) and (10) are satisfied by suitably selecting values 1, W0, W,, W W R, and R2, perfect balancing on XY plane will be obtained.

However, in actual mechanism, masses are distributed in the direction of Z axis, balancing condition of inertia forces in the direction of Z axis is necessary. The balancing condition of rotation and revolution masses in the direction of Z axis will be described. As shown in FIG. 3,

W reciprocating weight W rotation weight W rotation balance weight on left side W rotation balance weight on right side W total rotation weight XX axis of rotation shaft XJQ axis of big end of connecting rod YY: longitudinal axis of cylinder 0,: center of gravity of W 0 center of big end of connecting rod R distance between center of gravity of W and rotation axis R distance between center of gravity of W and rotation axis 1 distance between axis of big end of connecting rod and rotation axis I, distance between axis of cylinder and center of gravity L,: distance between centers of gravity of W., and W As it can be assumed that center of gravity of reciprocating weight W0, is at point 0 balancing condition of rotation is LtW8 W EEQUEQLQEIXQF by W4, W5, R4 and R5 V Total rotation weight W is W F W0+ W1 W0+ W4+ W5 Balancing condition of revolution will be described. In FIG. 4,

W revolution balance weight on left side W revolution balance weight on right side 22 axis of revolution shaft XX axis of rotation shaft YY: axis of center of gravity of W 0,: position of center of gravity of W R,,: distance between center of revolution and center of gravity of W,; R distance between center of revolution and center of gravity of W,

l distance between center of rotation and center of revolutron l distance between axis of center of gravity of W,,,, and

center of gravity of W, L distance between centers of gravity of W and W As it can be assumed that centerof gravity of total rotation weight W is at point 0,, balancing condition of revolution is Thus, perfect balance in the direction of Z axis will be obtained by suitably selecting W W,,, W W W W 1, 1,, L,, L,, R,, R,,, R, and R, to satisfy balancing condition of inertia forces in the direction of Z axis shown by formulas (l3) through (17).

As basic principles of linear reciprocating motion obtained by combination of circular motions and perfect balancing of the mechanism according to the invention are described, two

rod 1 to rotation of the eccentric collar 5 having angular velocity to; therotation is transmitted through the rotation spur gear 13 which is secured to the eccentric collar 5 to the eccentric gear 19 which is secured to the eccentric gear shaft 17 with eccentricity l and having the same number of teeth with the rotation spur gear 13. Rotation of the eccentric gear 19 is transmitted through the secured eccentric gear shaft 17 and the gear 20 which is also secured to the shaft 17 to the reduction gear 21 which is secured to the reduction gear shaft embodiments of perfectly balanced vibrationless rotationreciprocation device according to the invention will be described.

FIGS. 5 and 6 show a two-cycle reciprocating engine providing eccentric gear mechanism-While this is used as an example to describe the invention, it will-be understood that the invention has applications to almost all reciprocating machines or mechanisms to attain reciprocating motion by rotating motive power such as compressors, riveters, chisels, reciprocating cutters, spring testing machines, high speed fatigue testing machines, or beating motion mechanism of weaving machines, and to attain rotating motion by reciprocating motive power such as two-cycle or four-cycle gasoline or diesel engine.

As shown in H0. 5, big end of a linear reciprocating rod 1 providing a piston 2 which is slidably engaged in a cylinder 3, is rotatably supported through a plane bearing means 12 by an eccentric collar 5 which is rotatably supported through needle bearing means 6 by a crankpin 10 of a crankshaft 4.

I A seal 7 is secured toa casing 'to slidably engage the linearly reciprocating rod 1 to define an enclosed chamber 8 in the cylinder3 between the seal 7 and the piston 2. The cylinder 3 provides aspark plug 9 to the cylinder head portion 3'.

The eccentric collar 5 is supported by a crankpin 10 which is secured by crank arms 11 of the crankshaft 4. To one end of the eccentric collar 5 a rotation spur gear 13 is secured to rotate with the collar 5 about the axis of the crankpin 10. The crankshaft 4 is rotatably supported by ball bearings 14 which are supported by the casing 15. A revolution spur gear 16 is secured to one end portion of the crankshaft 4. An eccentric gear shaft17 and a reduction gear shaft 18 are rotatably supported by the casing 15 respectively. An eccentric gear 19 is secured to the eccentric gear shaft 17 and meshes with the rotation spur gear 13. A spur gear 20 is secured to the eccentric gear shaft 17 and meshes with a reduction gear 21 which is secured to the reduction gear shaft 18 and in turn meshes with the revolution spur gear 16 secured to the crankshaft 4. Thus, rotation of the crankshaft 4 can be transmitted to the eccentric collar 5. Y

As shown in FIGS. 5 and 6, in the lower portion of the cylinder 3 an inlet port 22 is provided to introduce gas mixture to the lower chamber 8, an exhaust port 23 is provided to exhaust spent gas and scavenge passage 24 are provided to supply compressed gas mixture to combustion space.

Operation of the two-cycle reciprocating engine shown in FIGS. 5 and 6 is as follows: I i I As the piston 2 moves upwards, the inlet port is opened to introduce gas mixture to the chamber 8, and at the same time gas mixture which has supplied to the combustion chamber is compressed by the piston 2. By combustion of the gas mixture ignited by the spark plug 9, the piston 2 is forced downwards, and spent gas is exhausted from the exhaust port 23. The downward movement of the piston 2 compresses the gas mixture in the chamber 8 and the precompressed gas mixture is supplied to the combustion chamber through scavenger passages 24. Thus, as to the operation, the two-cycle reciprocating engine according to the invention is similar to known crankcase compression two-cycle engine.

The thermal energy produced in'the combustion chamber is transmitted through the piston 2 and the linearly reciprocating 18. The reduction gear 21 in turn transmits the rotation to the crankshaft 4 through the gear 16 which is secured to the crankshaft 4 and having the same number of teeth with the gear 20. Thus, the crankshaft 4 rotates at angular velocity in in the reverse direction of the rotation spur gear 13 which is supported by the crankpin 10 having center axis 0, at eccentricity I from the crankshaft center axis 0. Consequently, the spur gear 13 rotates on the axis 0, and revolves on the axis 0 in the reverse direction and at the same angular velocity. As shown previously, as center 0, of the rotation eccentric collar 5 is on the longitudinal axis of the rod 1 and is at the distance 2! from the axis 0, the center 0, performs linear reciprocating motion having stroke 41; the linear. reciprocating motion is transmittcd through the gears l3, 19, 20 21 and 16 to the crankshaft 4 as rotation.

Balancing of the reciprocating engine shown in FIGS. 5 and 6 is described. As shown in F IG. 5, the rotation eccentric collar 5 provides to both sides of the roll 1 left and right rotation balance weights W, and W, in the reverse side of the eccentricity of the collar 5 about the axis 0,. The crank arms 11 of the crankshaft 4 respectively provide revolution balance weights W and W, in the reverse side of the crankpin 10 about the axis 0. The balance weights W W W and W, are determined, according to the invention, to satisfy above-mentioned formulas (9), l0) and(l3) through (17), i.e.,

W,,,,I=W,R,=W,R,,+ W,R,. The balance weights are secured to the eccentric collar 5 and the crank arms 11 as weights W, and W, at distances R, and R,

between the center of gravity and the axis, or as weights W,, W W, and W, at distances R R R and R Thus, as described before the reciprocating engine is perfectly balanced. ln the formulas W is the reciprocating weight, W is rotating weight,

I is an amount of eccentricity, l, is a distance between center of gravity of W, and axis of cylinder, 1, is distance between axis of center of gravity of W,,,, and center of gravity of W,, L, is distance between centers of gravity .of W, and W,,, and L is distance between centers of gravity of W, and W As a two-cycle engine, the reciprocating machine shown in FlGS. 5 and 6 has advantages that, the engine is perfectly balanced, and the vibration amplitude characteristic is in an order of 3-4u at 5,000 rpm. of the crankshaft, which is about one-eightieth of ordinary engine, so that the engine is especially suitable for engines without rigid foundation, such as portable engines. Further, as the connecting rod 1 reciprocateslinearly, lower space of the cylinder 3 can be sealed from crankcase space by the seal 7, so that the defined chamber 8 can be utilized as other-compression chamber. The compression ratio of the chamber 8 can very easily be accommodated to any desired value, so that effective scavenging can be attained.-

FIGS. 7 and 8 show another embodiment of the present invention utilizing internal geared transmitting mechanism. FIGS. 7 and 8 also show two-cycle reciprocating engine for the sake of clarity and to simplify description. The same reference numerals are used to represent similar parts or portions. Big end of a linearly reciprocating rod 1' is supported through a bearing means 12' b y an eccentric collar 5 which in turn is supported through needle bearing means 6 by a crankpin 10 of a crankshaft 4'. A planet gear 26 is secured to one end of the eccentric collar 5'. The crankshaft 4 is rotatably supported through ball bearings 14' by a portion of a casing 15. The planet gear 26 meshes with an internal gear 27 having twice number of teeth to the gear 26 and secured to the casing 15. The axis of the internal gear 27 coincides with the axis of the crankshaft 4, and the axis of the planet gear 26 coincides with the axis of the crankpin 10'. As before, the eccentric collar 5' provides to both sides of the rod 1' left and right rotation balance weights W and W, in the reverse side of the eccentricity of the collar 5 about the axis 0,. The crank arms 11 of the crankshaft 4' respectively provide revolution balance weights W and W in the reverse side of the crankpin 10' about the axis 0. Balance weights W W W and W are determined to satisfy above-mentioned formulas (9), (l) and l3) through (17).

Operation of the two-cycle internal combustion engine shown in FlGS. 7 and 8 is utterly similar to the engine shown in FIGS. and 6.

As the piston 2 moves upwards, the inlet port 22 is opened to introduce gas mixture to the chamber 8 and at the same time gas mixture which has supplied to the combustion chamber is compressed. By combustion of the gas mixture, the piston 2 is forced downwards and .thermal energy produced in the combustion chamber is transmitted through the piston 2 and the linearly reciprocating rod 1' to rotation of the eccentric collar 5'. As the axis of the planet gear 26 having pitch circle diameter 21 and secured to or integral with the eccentric collar 5' coincides with the axis of the crankpin and as the planet gear 26 meshes with the internal gear 27 which is secured to the casing and having twice number of teeth with that of the planet gear 26, axis 0 of the eccentric collar 5' aligns to a point on the periphery of the pitch circle of the internal gear 27 having pitch circle diameter 41 and reciprocates linearly. The crankshaft 4 acts as planet carrier of the planet gear 26 and rotates on the axis of the internal gear 27.

Thus, as above-mentioned mechanism, linear reciprocating motion of the connecting rod 1' is performed, and the reciprocating motion is transmitted to the rotation of the planet gear 26 meshing with the internal gear 27 about the axis 0 of the crankpin 10 to effect rotation of the eccentric collar 5' of angular velocity a: on the center axis 0 At the same time, the crankpin l0 revolves on the crankshaft axis 0 at the same angular velocity at and in the reverse direction to the eccentric collar 5'. Consequently, theeccentric collar 5 rotates on the axis 0 and revolves on the axis 0 at the same angular velocity and in the reverse direction each other. Balancing of this device is the same in the case of reciprocating engine providing eccentric gear mechanism (as shown in FIGS. 5 and 6). Thus, a simpler mechanism compared to the mechanism shown in FIGS. 5 and 6 is obtained to attain perfectly balanced rotation-reciprocation machine according to the invention.

Also in this case, the application of the device and the balancing theory is not limited to the shown two-cycle reciprocating engine or other engines to drive the output shaft. The same device can be used to be driven by input shaft, such as compressors, riveters, high speed fatigue testing machines, or other machines or mechanisms to attain reciprocating motion without vibration from rotating motive power source.

lclaim:

tricity l, means to cooperate said eccentric collar means and said crankshaft to rotate said crankshaft and collar means at the same constant angular velocity and in the reverse direction each other and to effect linear reciprocating motion of the rod, balance weight means having weights W, and W respectively secured to the eccentric collar in the opposite side of the center of the eccentric collar at distances R, and R to the axis of the crankpin and at distances (L -I and I, from longitudinal axis of the rod respectively, another balance weight means having weights W and W, respectively secured to each crank arms of the crankshaft in the opposite side of the crankpin atdistances R and R, from the axis of the crankshaft and at distances (Lg 2) and 1 from longitudinal axis of the rod respectively, and said both balance weight means being determined to satisfy formulae L2 e 6 z( 0+ a+ 4+ W5), wherein W, being reciprocating weight, W being rotating weight, L being distance between centers of gravity of W and W L being distance between centers of gravity of W and W so that unbalanced forces caused by reciprocating mass are balanced.

2. A rotation-reciprocation device claimed in claim 1, wherein said means to cooperate the eccentric collar and the crankshaft comprising a first gear secured to the eccentric collar, a first and a second shafts rotatably supported by the casing and being parallel to the axis of the crankshaft,an eccentric gear having the same number of teeth with that in the first gear and the amount of eccentricity l and being secured to the first shaft and meshing with the first gear, a second gear secured to the first shaft, a third gear supported by the second shaft and meshing with the second gear, a fourth gear secured to the crankshaft and meshing with the third gear and having the same number of teeth with that in the second gear.

3. A rotation-reciprocation device claimed in claim 1, wherein said means to cooperate the eccentric collar and the crankshaft comprising planet gear means having pitch-circle diameter 2l and being secured to the eccentric collar to rotate on the crankpin, and internal gear means secured to the casing to be concentric to the crankshaft axis and meshing with the planet gear means and having pitch circle diameter 4!.

4. A rotation-reciprocation device claimed in any of preceding claims in which said working means connected to one end of the rod being piston means, and the device further comprising cylinder means accommodating said piston means and defining combustion chamber between the piston means, said piston means having inlet, outlet and scavenging passage means and being connected to the casing, spark plug means mounted to the cylinder means, seal means secured to the casing and slidably engaging said rod to define a further space in the cylinder means between said piston and said casing, and said inlet means and one end of the scavenging passage means being communicated to said further space whereby the device is formed as two-cycle internal combustion engine and the further space is formed as precompression chamber of the engme. 

2. A rotation-reciprocation device claimed in claim 1, wherein said means to cooperate the eccentric collar and the crankshaft comprising a first gear secured to the eccentric collar, a first and a second shafts rotatably supported by the casing and being parallel to the axis of the crankshaft, an eccentric gear having the same number of teeth with that in the first gear and the amount of eccentricity -l and being secured to the first shaft and meshing with the first gear, a second gear secured to the first shaft, a third gear supported by the second shaft and meshing with the second gear, a fourth gear secured to the crankshaft and meshing with the third gear and having the same number of teeth with that in the second gear.
 3. A rotation-reciprocation device claimed in claim 1, wherein said means to cooperate the eccentric collar and the crankshaft comprising planet gear means having pitch circle diameter 2l and being secured to the eccentric collar to rotate on the crankpin, and internal gear means secured to the casing to be concentric to the crankshaft axis and meshing with the planet gear means and having pitch circle diameter 4l.
 4. A rotation-reciprocation device claimed in any of preceding claims in which said working means connected to one end of the rod being piston means, and the device further comprising cylinder means accommodating said piston means and defining combustion chamber between the piston means, said piston means having inlet, outlet and scavenging passage means and being connected to the casing, spark plug means mounted to the cylinder means, seal means secured to the casing and slidably engaging said rod to define a further space in the cylinder means between said piston and said casing, and said inlet means and one end of the scavenging passage means being communicated to said further space whereby the device is formed as two-cycle internal combustion engine and the further space is formed as precompression chamber of the engine. 